Voltage regulators, such as DC-to-DC voltage converters, are used to provide stable voltage sources for various electronic systems. Efficient DC-to-DC converters are particularly needed for battery management in low power devices (e.g., laptop notebooks, cellular phones, etc.). A switching voltage regulator generates an output voltage by converting an input DC voltage into a high frequency voltage, and then filtering the high frequency input voltage to generate the output DC voltage. Specifically, the switching regulator includes a switch for alternately coupling and decoupling an input DC voltage source (e.g., a battery) to a load (e.g., an integrated circuit (IC)). An output filter, typically including an inductor and a capacitor, may be coupled between the input voltage source and the load to filter the switch output, and thus provide the output DC voltage. A controller (e.g., a pulse width modulator (PWM), a pulse frequency modulator, etc.) can be used to control the switch to maintain a substantially constant output DC voltage.
Traditional switching regulators use a transconductance amplifier or operational amplifier as an error amplifier for amplifying a difference between an output feedback level and a reference level. To stabilize the regulation loop, a transfer function of such an error amplifier should be designed to accommodate the poles and zeroes in a regular power stage transfer function. However, the power stage transfer function in a switching regulator often varies with the operation conditions (e.g., input voltage, output current, etc.). Thus, the transfer function of the error amplifier might be conservatively designed in switching regulators to achieve good stability margin under all operation conditions, resulting in relatively poor transient responses.